Will Quantum Computing Break Bitcoin?

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  • Quantum computing is thought by many to have the ability to cripple the Bitcoin blockchain
  • However powerful the first quantum computers might be, the financial and logistical hurdles amount to a much reduced concern
  • Rogue quantum computers will more likely target government or military networks first

Quantum computing has long been feared as Bitcoin’s mortal enemy – the Lex Luther to Bitcoin’s Superman. But, what is quantum computing, and what are the risks to Bitcoin and other cryptocurrencies? Should we be worried, or is this the Millennium Bug of the crypto world? We peek behind the quantum curtain to find out.

What is Quantum Computing?

Simply speaking, quantum computers are computers that use ‘qubits’ (quantum bits) instead of regular bits to perform their calculations. This means they can run computations at stupidly fast speeds – D-Wave’s 2X quantum computer, for example, is 100 million times faster than an average laptop. It’s fairly easy to see why companies and government agencies would like to get their hands on quantum computers, and the likes of NASA, Google and Lockheed Martin have already done just that, spending $10-$15 million per machine, but these are the very first iterations of the technology and are still very much at the experimental stage.

What’s The Threat to Bitcoin?

Quantum computing is causing fear among the Bitcoin community because, in theory at least, it has the power to crack Bitcoin’s SHA256 cryptography encryption. The theory goes that quantum computers will be able to run the 1283 basic operations required to break the Shor Algorithm that prevents a Bitcoin public key from being associated with its private key, allowing perpetrators the match them up and obtain countless private keys.

There is a separate threat from the mining power of a quantum computer being able to monopolize the Bitcoin hashing power, but this is less of a concern given the constant evolution of ASIC miners.

How Likely Is This to Happen?

Theory and practice are two very different things, and with quantum computers at such an early stage we are, in the words of Gizmodo’s Ryan F. Mandelbaum, “probably several decades away” from encryption strategies being hacked by quantum computers. This is because the early versions of quantum computers are going to be too slow, too difficult to operate, and too physically imposing for many would-be hackers to utilize for many years after they become mainstream.

Even if the hardware exists, it needs the right software to point the supercomputer in the direction of hacking Bitcoin, and this is even further away. Cryptography standards such as ECRYPT II tend to say that Bitcoin’s 256-bit ECDSA keys are secure until at least 2030-2040, while Dr. Gavin Brennan, a quantum physicist at Macquarie University in Sydney, Australia, made the following claim in a 2017 paper ‘Quantum Attacks on Bitcoin, and How to Protect Against Them’:

We find that the proof-of-work used by Bitcoin is relatively resistant to substantial speedup by quantum computers in the next 10 years, mainly because specialized ASIC miners are extremely fast compared to the estimated clock speed of near-term quantum computers.

Don’t Panic!

While quantum computing is coming, its risk to Bitcoin, and other encryption mechanisms, is low. Also, even if a quantum computer were made ready to attack Bitcoin, it would need to be able to break your key in the short time between when your transaction is first sent and when it gets into a block. Quantum computing’s perceived threat will make headlines in the coming years, but in truth it’s ability to bring down the Bitcoin network is both minimal and decades away, if it ever happens.